rs200716018

Variant names:

• chr2-178530049-T-C
• rs200716018
• NM_001267550.2:c.106442A>G

Variant summary

Our verdict is Likely benign. Variant got -3 ACMG points: 0P and 3B. BP4_Moderate BP6

The NM_001267550.2(TTN):​c.106442A>G​(p.Lys35481Arg) variant causes a missense change. The variant allele was found at a frequency of 0.000161 in 1,611,666 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a benign outcome for this variant. 14/19 in silico tools predict a benign outcome for this variant. Variant has been reported in ClinVar as Conflicting classifications of pathogenicity (no stars).

• Frequency:
  • Genomes: 𝑓 0.00011 (0 hom., cov: 33)
  • Exomes 𝑓: 0.00017 (0 hom.)
• Consequence: TTN NM_001267550.2 missense
• Clinical Significance: Conflicting classifications of pathogenicity criteria provided, conflicting classifications U:11 B:3
• Conservation: PhyloP100: 5.47

Genes affected

TTN (HGNC:12403): (titin) This gene encodes a large abundant protein of striated muscle. The product of this gene is divided into two regions, a N-terminal I-band and a C-terminal A-band. The I-band, which is the elastic part of the molecule, contains two regions of tandem immunoglobulin domains on either side of a PEVK region that is rich in proline, glutamate, valine and lysine. The A-band, which is thought to act as a protein-ruler, contains a mixture of immunoglobulin and fibronectin repeats, and possesses kinase activity. An N-terminal Z-disc region and a C-terminal M-line region bind to the Z-line and M-line of the sarcomere, respectively, so that a single titin molecule spans half the length of a sarcomere. Titin also contains binding sites for muscle associated proteins so it serves as an adhesion template for the assembly of contractile machinery in muscle cells. It has also been identified as a structural protein for chromosomes. Alternative splicing of this gene results in multiple transcript variants. Considerable variability exists in the I-band, the M-line and the Z-disc regions of titin. Variability in the I-band region contributes to the differences in elasticity of different titin isoforms and, therefore, to the differences in elasticity of different muscle types. Mutations in this gene are associated with familial hypertrophic cardiomyopathy 9, and autoantibodies to titin are produced in patients with the autoimmune disease scleroderma. [provided by RefSeq, Feb 2012]

TTN-AS1 (HGNC:44124): (TTN antisense RNA 1) This gene encodes a non-coding RNA transcribed from the opposite strand to the titin gene. [provided by RefSeq, Aug 2016]

ACMG classification

Verdict is Likely_benign. Variant got -3 ACMG points.

• BP4: Computational evidence support a benign effect (MetaRNN=0.16418725).
• BP6: Variant 2-178530049-T-C is Benign according to our data. Variant chr2-178530049-T-C is described in ClinVar as [Conflicting_classifications_of_pathogenicity]. Clinvar id is 284002.We mark this variant Likely_benign, oryginal submissions are: {Likely_benign=1, Benign=2, Uncertain_significance=10}.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
TTN	NM_001267550.2	c.106442A>G	p.Lys35481Arg	missense_variant	Exon 359 of 363	ENST00000589042.5	NP_001254479.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
TTN	ENST00000589042.5	c.106442A>G	p.Lys35481Arg	missense_variant	Exon 359 of 363	5	NM_001267550.2	ENSP00000467141.1

Frequencies

GnomAD3 genomes AF: 0.000105 AC: 16 AN: 152196 Hom.: 0 Cov.: 33

Gnomad AFR AF: 0.0000241

Gnomad AMI AF: 0.00

Gnomad AMR AF: 0.00

Gnomad ASJ AF: 0.00

Gnomad EAS AF: 0.00

Gnomad SAS AF: 0.00

Gnomad FIN AF: 0.00

Gnomad MID AF: 0.00

Gnomad NFE AF: 0.000221

Gnomad OTH AF: 0.00

GnomAD3 exomes AF: 0.0000405 AC: 10 AN: 247170 Hom.: 0 AF XY: 0.0000373 AC XY: 5 AN XY: 134010

Gnomad AFR exome AF: 0.0000647

Gnomad AMR exome AF: 0.0000294

Gnomad ASJ exome AF: 0.00

Gnomad EAS exome AF: 0.00

Gnomad SAS exome AF: 0.00

Gnomad FIN exome AF: 0.00

Gnomad NFE exome AF: 0.0000623

Gnomad OTH exome AF: 0.000167

GnomAD4 exome AF: 0.000166 AC: 243 AN: 1459470 Hom.: 0 Cov.: 32 AF XY: 0.000152 AC XY: 110 AN XY: 725848

Gnomad4 AFR exome AF: 0.00

Gnomad4 AMR exome AF: 0.00

Gnomad4 ASJ exome AF: 0.00

Gnomad4 EAS exome AF: 0.00

Gnomad4 SAS exome AF: 0.00

Gnomad4 FIN exome AF: 0.00

Gnomad4 NFE exome AF: 0.000200

Gnomad4 OTH exome AF: 0.000348

GnomAD4 genome AF: 0.000105 AC: 16 AN: 152196 Hom.: 0 Cov.: 33 AF XY: 0.0000941 AC XY: 7 AN XY: 74356

Gnomad4 AFR AF: 0.0000241

Gnomad4 AMR AF: 0.00

Gnomad4 ASJ AF: 0.00

Gnomad4 EAS AF: 0.00

Gnomad4 SAS AF: 0.00

Gnomad4 FIN AF: 0.00

Gnomad4 NFE AF: 0.000221

Gnomad4 OTH AF: 0.00

Alfa AF: 0.0000797 Hom.: 0

Bravo AF: 0.0000907

TwinsUK AF: 0.000539 AC: 2

ALSPAC AF: 0.00 AC: 0

ESP6500AA AF: 0.000277 AC: 1

ESP6500EA AF: 0.000123 AC: 1

ExAC AF: 0.0000248 AC: 3

EpiCase AF: 0.000328

EpiControl AF: 0.0000593

ClinVar

Significance: Conflicting classifications of pathogenicity

Submissions summary: Uncertain:11 Benign:3

Revision: criteria provided, conflicting classifications

Submissions by phenotype

not provided Uncertain:3 Benign:1

May 03, 2021

GeneDx

Significance: Likely benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant is associated with the following publications: (PMID: 31983221) -

Dec 23, 2020

Revvity Omics, Revvity

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Jan 11, 2017

Eurofins Ntd Llc (ga)

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dec 14, 2023

ARUP Laboratories, Molecular Genetics and Genomics, ARUP Laboratories

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The TTN c.106442A>G; p.Lys35481Arg variant (rs200716018; ClinVar Variation ID: 284002) is rare in the general population (<0.2% allele frequency in the Genome Aggregation Database) and has been reported in one individual with dilated cardiomyopathy (Mazzarotto 2020). The clinical relevance of rare missense variants in this gene, which are identified on average once per individual sequenced in affected populations (Herman 2012), is not well understood. Yet, evidence suggests that the vast majority of such missense variants do not contribute to the clinical outcome of DCM (Begay 2015). Thus, the clinical significance of the p.Lys35481Arg variant cannot be determined with certainty. References: Begay RL et al. Role of Titin Missense Variants in Dilated Cardiomyopathy. J Am Heart Assoc. 2015 Nov 13;4(11). PMID: 26567375. Herman DS et al. Truncations of titin causing dilated cardiomyopathy. N Engl J Med. 2012 Feb 16;366(7):619-28. PMID: 22335739. Linke WA and Hamdani N. Gigantic business: titin properties and function through thick and thin. Circ Res 2014; 114(6): 1052-1068. PMID: 24625729. Mazzarotto F et al. Reevaluating the Genetic Contribution of Monogenic Dilated Cardiomyopathy. Circulation. 2020 Feb 4;141(5):387-398. PMID: 31983221. -

not specified Uncertain:1

Jan 03, 2024

Women's Health and Genetics/Laboratory Corporation of America, LabCorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

Variant summary: TTN c.98738A>G (p.Lys32913Arg) results in a conservative amino acid change located in the M-band domain of the encoded protein sequence. Four of five in-silico tools predict a benign effect of the variant on protein function. The variant allele was found at a frequency of 4e-05 in 247170 control chromosomes. To our knowledge, no occurrence of c.98738A>G in individuals affected with Limb-Girdle Muscular Dystrophy, Type 2J and no experimental evidence demonstrating its impact on protein function have been reported. Eight submitters have cited clinical-significance assessments for this variant to ClinVar after 2014, classifying the variant as uncertain significance (n=5) or likely benign (n=1). Based on the evidence outlined above, the variant was classified as uncertain significance. -

TTN-related disorder Uncertain:1

Mar 03, 2024

PreventionGenetics, part of Exact Sciences

Significance: Uncertain significance

Review Status: no assertion criteria provided

Collection Method: clinical testing

The TTN c.106442A>G variant is predicted to result in the amino acid substitution p.Lys35481Arg. This variant was reported in an individual with dilated cardiomyopathy (Table S3, Mazzarotto et al. 2020. PubMed ID: 31983221). This variant is reported in 0.0083% of alleles in individuals of African descent in gnomAD (http://gnomad.broadinstitute.org/variant/2-179394776-T-C). At this time, the clinical significance of this variant is uncertain due to the absence of conclusive functional and genetic evidence. -

Autosomal recessive limb-girdle muscular dystrophy type 2J Uncertain:1

May 17, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Autosomal recessive limb-girdle muscular dystrophy type 2J;C1858763:Dilated cardiomyopathy 1G Uncertain:1

Aug 22, 2017

Labcorp Genetics (formerly Invitae), Labcorp

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Cardiomyopathy Uncertain:1

Dec 07, 2020

CHEO Genetics Diagnostic Laboratory, Children's Hospital of Eastern Ontario

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

- -

Dilated cardiomyopathy 1G Uncertain:1

May 17, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Early-onset myopathy with fatal cardiomyopathy Uncertain:1

May 17, 2018

Illumina Laboratory Services, Illumina

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score, this variant could not be ruled out of causing disease and therefore its association with disease required further investigation. A literature search was performed for the gene, cDNA change, and amino acid change (if applicable). No publications were found based on this search. This variant was therefore classified as a variant of unknown significance for this disease. -

Cardiovascular phenotype Uncertain:1

May 16, 2018

Ambry Genetics

Significance: Uncertain significance

Review Status: criteria provided, single submitter

Collection Method: clinical testing

The p.K26416R variant (also known as c.79247A>G), located in coding exon 186 of the TTN gene, results from an A to G substitution at nucleotide position 79247. The lysine at codon 26416 is replaced by arginine, an amino acid with highly similar properties. This amino acid position is not well conserved in available vertebrate species. In addition, this alteration is predicted to be benign by PolyPhen in silico analysis. Since supporting evidence is limited at this time, the clinical significance of this alteration remains unclear. -

Tibial muscular dystrophy Benign:1

May 16, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Myopathy, myofibrillar, 9, with early respiratory failure Benign:1

May 16, 2018

Illumina Laboratory Services, Illumina

Significance: Benign

Review Status: criteria provided, single submitter

Collection Method: clinical testing

This variant was observed in the ICSL laboratory as part of a predisposition screen in an ostensibly healthy population. It had not been previously curated by ICSL or reported in the Human Gene Mutation Database (HGMD: prior to June 1st, 2018), and was therefore a candidate for classification through an automated scoring system. Utilizing variant allele frequency, disease prevalence and penetrance estimates, and inheritance mode, an automated score was calculated to assess if this variant is too frequent to cause the disease. Based on the score and internal cut-off values, a variant classified as benign is not then subjected to further curation. The score for this variant resulted in a classification of benign for this disease. -

Computational scores

Source: dbNSFP v4.3

Name	Calibrated prediction	Score	Prediction
AlphaMissense	Benign	0.098
BayesDel_addAF	Benign	-0.28	T
BayesDel_noAF	Benign	-0.45
CADD	Benign	17
DANN	Benign	0.74
Eigen	Benign	-0.20
Eigen_PC	Benign	-0.0026
FATHMM_MKL	Uncertain	0.93	D
LIST_S2	Benign	0.80	T;T;T;.;T;T;T
M_CAP	Benign	0.017	T
MetaRNN	Benign	0.16	T;T;T;T;T;T;T
MetaSVM	Benign	-1.0	T
MutationAssessor	Benign	0.57	.;.;.;N;.;.;N
PrimateAI	Benign	0.42	T
PROVEAN	Benign	-1.6	N;N;.;.;N;N;.
REVEL	Benign	0.14
Sift	Benign	0.089	.;T;.;.;T;T;.
Polyphen		0.16	.;.;.;B;.;.;B
Vest4		0.29
MVP		0.21
MPC		0.087
ClinPred		0.19	T
GERP RS		5.8

Splicing

Name	Calibrated prediction	Score	Prediction
SpliceAI score (max)		0.0		Details are displayed if max score is > 0.2

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

LitVar

Other links and lift over

dbSNP: rs200716018; hg19: chr2-179394776;